Study On Removal Of Antibiotic Chloramphenicol By Nanoscale Zero-Valent Iron In Water

Batch experiments were carried out to investigate the reaction mechanism and kinetics between different carbon/iron nanoparticles and antibiotic chloramphenicol（CAP）.Nanoscale zero-valent iron（nZVI）is very efficient in removing chlorinated nitroaromatic antibiotic CAP from water and wastewater.n ZVI and different carbon/iron nanoparticles were prepared,using a series of characterization methods including scanning electron microscope,transmission electron microscope,energy dispersive X-ray,X-ray diffraction,X-ray photoelectron spectroscopy to investigate the microstructure,element composition and structure features of the samples.Using high performance liquid chromatography（HPLC）and ultra performance liquid chromatography-mass mass spectrometry（UPLC-MS/MS）analysis to investigate the pathway and kinetics of CAP removal by n ZVI.nZVI showed a core-shell structure.Higher nZVI dosage and reaction temperature would promote the removal of CAP by n ZVI,while higher pH and ion strength would result in a negative effect on the removal of CAP by nZVI.The process of CAP removal could be divided into two stages according to the pseudo-first-order kinetic model.A total of 97.0%of 0.30 mM CAP was rapidly removed by 1.8 mM nZVI in the first stage（6 min）.The product distribution after reaction was also investigated.Based on the identification of four main reduction products via HPLC,UPLC-MS/MS,and nuclear magnetic resonance-H spectrums,a more detailed pathway of CAP degradation by nZVI was proposed than ever reported.The two O atoms on the-NO₂ group were successively reduced first,and then two Cl atoms were removed via dechlorination.Notably,after reaction with nZVI,the antibacterial activity of the CAP solution was greatly reduced.100%of CAP could be removed in the first two runs,while no degradation of CAP was observed due to the exhaust of Fe⁰ in the solution.Various carbons（activated carbon,biochar,carbon powder,multi-walled carbon nanotubes,and graphene oxide）were used to stabilize nZVI,and their performances for the removal of CAP were systematically investigated.The introduction of carbon matrix could promote the reactivity of nZVI for CAP removal.According to the comparisons of characterizations and reactivity of these nanocomposites,the removal rate of CAP was mainly affected by the distribution of nZVI particles,and the most dispersive nZVI particles with the support of carbon powder exhibited the highest reactivity.The reusability of carbon powder supported n ZVI nanocomposites were further investigated,and 100%of CAP could be removed in the first three runs,while no degradation of CAP was observed when the solution oxidation-reduction potential value was higher than-200 mV.Four products（CAP-O,CAP-2O,CAP-2O-Cl and CAP-2O-2Cl）were confirmed via UPLC-MS/MS analysis,and the entire pathway of CAP removal（including denitration and dichlorination）was elucidated.The antibacterial activities of CAP-contaminated solutions were all obviously decreased after the treatments by the five carbon-based nZVI nanocomposites used in this study.The aging time effect on the morphology and structure of n ZVI particles and CAP removal were investigated.Besides,batch experiments were performed to investigate the potential application of nZVI for CAP removal in different water matrices,including groundwater,river water,seawater,and wastewater.With the n ZVI aging time increasing,the surface of nZVI is passivated and Fe⁰ was gradually consumed,iron oxides were produced on the surface of nZVI.In the end,nZVI lost its original features and lost the ability to remove CAP on the day 21.The CAP removal efficiency and the rate both decline with the time.CAP can be effectively removed by nZVI in the first few minutes of the reaction in the groundwater,river water,seawater,and wastewater.